Lyme and other tick-borne diseases pose a significant health threat to outdoor workers. In a double - blind randomized controlled trial (RCT) in North Carolina outdoor workers, we previously showed that long-lasting permethrin-impregnated (LLPI) clothing provided >80% protection for one year against Lone Star tick bites among outdoor workers in North Carolina. But there are three issues that need to be addressed before this finding can be translated into policy: 1) Do LLPI clothing protect t against blacklegged ticks, the vector for Lyme disease, babesiosis and anaplasmosis, as well as against the Lone Star tick? 2) What levels of permethrin and its metabolites are absorbed, and are they potentially toxic? 3) Why did the LLPI clothing in our previous study lose efficacy after a year? To answer these questions, we propose a two year double-blind RCT with 200 outdoor workers in Lyme endemic areas of the Northeast. Outdoor workers from the National Park Service, the Rhode Island Department of Environmental Management, and NationalGrid will be randomly assigned to the treatment or control group. All study subjects will fill out weekly tick logs, collct attached ticks for later speciation and pathogen detection, and submit annual serum samples to test for exposure to tick-borne pathogens. A randomly selected subset of subjects also will be asked to submit urine samples for permethrin metabolite analysis at several time points during follow-up. Others will be asked to submit worn items of clothing for tick knockdown testing and permethrin content analysis at the end of the first and second years of field testing. This project specifically addresses the following NIOSH Priority Goals for Extramural Research: Goal 2: Reduce deleterious health and safety outcomes in workers more susceptible to injury or illness due to circumstances limiting options for safeguarding their own safety and health, Goal 7: Improve the health and well-being of forestry workers by reducing occupational causes or contributing factors to acute and chronic illness and disease. This research will address the agriculture, forestry, and fishing sector and personal protective technology cross-sector by evaluating the protective effectiveness and toxicological risk of long-lasting permethrin impregnated clothing for prevention of tick bites and tick-borne disease among forestry and utility workers and park rangers. The results of this study could help protect hundreds of thousands of outdoor workers with exposure to ticks and tick-borne pathogens.